U.S. patent number 4,642,221 [Application Number 06/510,502] was granted by the patent office on 1987-02-10 for method and composition for inhibiting corrosion in aqueous heat transfer systems.
This patent grant is currently assigned to Atlantic Richfield Company. Invention is credited to Joseph N. Biber, Gerald D. Hansen.
United States Patent |
4,642,221 |
Hansen , et al. |
February 10, 1987 |
Method and composition for inhibiting corrosion in aqueous heat
transfer systems
Abstract
Corrosion of metal surfaces in cooper or copper alloy cooling
water systems is inhibited by the addition of small amounts of
aromatic triazoles and iminodicarboxylic acids or derivatives
thereof to the cooling water system.
Inventors: |
Hansen; Gerald D. (Holicong,
PA), Biber; Joseph N. (West Chester, PA) |
Assignee: |
Atlantic Richfield Company (Los
Angeles, CA)
|
Family
ID: |
24031009 |
Appl.
No.: |
06/510,502 |
Filed: |
July 5, 1983 |
Current U.S.
Class: |
422/16; 252/180;
252/392 |
Current CPC
Class: |
C02F
5/12 (20130101); C23F 11/10 (20130101); C23F
11/149 (20130101); C02F 2303/08 (20130101); C02F
2103/023 (20130101) |
Current International
Class: |
C23F
11/14 (20060101); C23F 11/10 (20060101); C23F
011/04 () |
Field of
Search: |
;252/392,180
;422/16 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Terapane; John F.
Assistant Examiner: Thexton; Matthew A.
Attorney, Agent or Firm: Reap; Coleman R.
Claims
What is claimed is:
1. In a method of inhibiting corrosion of copper or copper alloy
metallic surfaces which are in contact with an aqueous liquid
containing hypochlorite ions by adding to the aqueous liquid an
aromatic triazole, the improvement comprising adding to the aqueous
liquid an imino compound having the structural formula
where R and R' are identical or different radicals selected from
saturated aliphatic carboxylic acid radicals having 2 to 6 carbon
atoms, saturated aliphatic carboxylic acid ester radicals having 2
to 6 acid moiety carbon atoms and 3 to 16 total carbon atoms, and
water soluble alkali or alkaline earth metal salts of saturated
aliphatic carboxylic acid radicals having 2 to 6 carbon atoms and
mixtures of these.
2. The improved method of claim 1 wherein the total amount of imino
compound in the aqueous medium is maintained in the range of about
0.01 to 250 ppm, based on the total weight of the aqueous medium
present.
3. The improved method of claim 1 wherein R and R' are saturated
aliphatic carboxylic acid radicals having 2 to 6 carbon atoms.
4. The improved method of claim 1 wherein the total amount of imino
compound present in the aqueous medium is maintained in the range
of about 0.1 to 50 ppm.
5. The improved method of any of claims 1, 2, 3 or 4 wherein said
aromatic triazole is selected from benzotriazole,
hydroxybenzotriazole, alkyl-substituted benzotriazoles having 1 to
6 alkyl carbon atoms and mixtures of these.
6. The improved process of claim 5 wherein the total amount of
aromatic triazole in the aqueous medium is maintained in the range
of about 0.01 to 250 ppm, based on the total weight of a aqueous
medium present.
7. The improved process of claim 6 wherein said aromatic triazole
is selected from benzotriazole, methylbenzotriazoles,
dimethyltriazoles, hydroxybenzotriazole and mixtures of these and
said imino compound is iminodiacetic acid.
8. A method of inhibiting corrosion of copper or copper alloy metal
surfaces in cooling water systems comprising maintaining in the
cooling water about 0.01 to 250 ppm of an aromatic triazole
selected from benzotriazole, hydroxybenzotriazole,
methylbenzotriazoles, dimethyltriazoles and mixtures of these and
about 0.01 to 250 ppm of an iminodicarboxylic acid selected from
iminodiacetic acid, iminodipropionic acid, iminodibutyric acid,
iminodipentanoic acid, iminodihexanoic acid, and mixtures of
these.
9. The method of claim 8 wherein said aromatic triazole is
benzotriazole, methylbenzotriazole or mixtures of these and it is
maintained in the cooling water at a concentration of about 0.1 to
50 ppm and said iminodicarboxylic acid is iminodiacetic acid and it
is maintained in the cooling water at a concentration of 0.1 to 50
ppm.
Description
BACKGROUND OF THE INVENTION
This invention relates to the inhibition of corrosion of metal
surfaces and more particularly to the inhibition of corrosion of
copper or copper alloy surfaces in heat transfer equipment.
Metal surfaces which are in continuous contact with water or
aqueous liquids, particularly aqueous liquids that contain
chemicals or mineral salts, generally undergo considerable
corrosion. To extend the life of the metal surfaces it is common
practice to add small amounts of certain chemical substances to the
aqueous liquid to inhibit corrosion of the metal surfaces.
Copper metal and copper alloys, which are often used in heat
transfer equipment because of their superior heat transfer
properties, are particularly susceptible to corrosion. One class of
organic compounds, the aromatic triazoles, have been found to be
quite effective in inhibiting the corrosion of copper metal. The
triazole molecule appears to form a complex with the copper on the
surfaces of the metal thereby forming a coating on the metal
surfaces which protects the surfaces from the effects of corrosive
materials. Several patents and literature references describe the
use of aromatic triazoles alone or in combination with other
chemical compounds as corrosion inhibitors. U.S. Pat. No.
3,265,620, issued to Heiman, discloses metal working coolants
containing diethanolamine, benzotriazole and the tetrasodium salt
of ethylene diaminetetraacetic acid. U.S. Pat. No. 3,291,741,
issued to Maciejewski et al, discloses an anticorrosive composition
comprised of, inter alia, benzotriazole and 4,4-bis(3-nitro-4
hydroxyphenyl)pentanoic acid. U.S. Pat. No. 4,197,210, issued to
Bridger, discloses a lubricant composition comprised of an
oil-soluble adduct of benzotriazole and a dialkylamine. U.S. Pat.
No. 3,553,137, issued to Woods, discloses a three component
corrosion inhibitor for methoxypropanol comprised of an alkali
metal nitrite, a piperazine and benzotriazole. Polish Pat. Nos.
90115 (see Chemical Abstract 90:74229m) and 95752 (see Chemical
Abstract 91:23747s) disclose mining apparatus hydraulic fluids
containing benzotriazole and an emulsifying oil containing
diethanolamine. Razrab. Mer Zashch. Met. Korroz., Mezhdunar.
Nauchno-Tekk. Konf. Probl. SEV. 3rd, 1980, 3, 47-50 (see Chemical
Abstract 95:136895q) discloses a volatile corrosion inhibitor
comprised of hydroxybenzotriazole and diethanolamine. Japanese Pat.
No. 57049677 and Japanese Pat. No. 8249677 disclose
methylbenzotriazole amine and diethanolamine benzotriazole salts as
corrosion inhibitors for aqueous inks. Japanese Pat. No. 8223071
discloses a cooling system corrosion inhibitor comprised of
benzotriazole and diethanolamine. Japanese patent application
8017864 discloses a corrosion inhibitor for wire enamels comprised
of the diethanolamine salt of benzotriazole. British Pat. No.
2,080,342 discloses a composition for improving rust resistance
comprised of an aliphatic dicarboxylic acid and
1-hydroxybenzotriazole.
Quite often there is a tendency for bacteria to accumulate and
multiply in cooling water systems. To counteract the growth of
bacteria, water soluble hypochlorites, such as sodium hypochlorite
and other chlorine-containing compounds which form hypochlorite
ions, are added to the cooling water. Although these compounds are
effective biocides, they interfere with the aromatic triazole,
apparently by combining with the triazole. Another problem
encountered in the use of aromatic triazoles in cooling water
systems is that the cooling water often contains small amounts of
copper ions. These copper ions also combine with the aromatic
triazoles thereby reducing the amount of aromatic triazole that is
available for the protection of the metal surface.
Because of the effectiveness of aromatic triazoles in inhibiting
corrosion of metal surfaces it would be desirable to eliminate the
interference of chlorine-containing compounds with the corrosion
inhibiting effectiveness of aromatic triazoles. It would be very
beneficial if the interference of both chlorine-containing
compounds and copper ions with the effectiveness of the triazoles
could be eliminated at the same time.
SUMMARY OF THE INVENTION
Corrosion inhibiting compositions which contain aromatic triazoles
and which are substantially free from interference by hypochlorite
and copper ions have now been discovered. Accordingly, it is an
object of the invention to present improved aromatic triazole-based
corrosion inhibitors. It is another object of the invention to
present aromatic triazoles containing corrosion inhibiting
compositions which are substantially free from interference by
hypochlorite ions. It is another object of the invention to present
aromatic triazole-containing corrosion inhibitors which are
substantially free from interference by copper ions. It is another
object of the invention to present an improved method of inhibiting
corrosion of copper metal or copper alloy cooling water systems. It
is another objective to present a method of substantially
eliminating the interference of hypochlorite ions and copper ions
with the corrosion-inhibiting activity of aromatic
triazole-containing corrosion inhibiting compositions. These and
other objects of the invention are supported in the following
description and examples.
The above objects are achieved in the new compositions of this
invention, which comprise one or more aromatic triazoles and one or
more imines of a carboxylic acid, a carboxylic acid ester, a
water-soluble salt of a carboxylic acid or mixtures of any of
these. In a preferred embodiment the aromatic triazole is
benzotriazole or an alkylbenzotriazole and the imine compound is an
imine dicarboxylic acid.
DETAILED DESCRIPTION OF THE INVENTION
The aromatic triazoles useful in the invention are any of the
aromatic triazoles which have corrosion inhibiting activity. These
include benzenetriazole and derivatives of benzotriazoles, such as
alkyl-substituted triazoles, hydroxy-substituted benzotriazoles,
halogen-substituted benzotriazoles, etc. The alkylbenzotriazoles
which are commonly used as corrosion inhibitors are those having 1
to 8 alkyl carbon atoms. Although alkylbenzotriazoles having more
than about 8 alkyl carbon atoms and higher aromatic triazoles, such
as naphthotriazole, can be used in the invention, these compounds
are less desirable because of their higher cost or because they are
not readily commercially available. Preferred alkylbenzotriazoles
are those having 1 to 6 alkyl carbon atoms. Other substituted
benzotriazole compounds include hydroxybenzotriazoles. Examples of
suitable aromatic triazoles are benzotriazole, methylbenzotriazole,
dimethylbenzotriazole, ethylbenzotriazole, diethylbenzotriazole,
hydroxybenzotriazole, methylhydroxybenzotriazole, etc.
The imino compounds useful in the invention have the structural
formula
wherein R and R' are identical or different carboxylic acid
radicals, carboxylic acid ester radicals, alkali or alkaline earth
metal salts of carboxylic acid radicals or mixtures of these.
Carboxylic acid radicals suitable for use in the invention are the
saturated or ethylenically unsaturated aliphatic mono- or
polycarboxylic acid radicals and aromatic mono- or polycarboxylic
acid radicals. The water-soluble lower molecular weight carboxylic
acid radicals are preferred for applications in aqueous systems,
while the oil-soluble higher molecular weight carboxylic acid
radicals are useful in systems comprised substantially of
petroleum-based liquids. Carboxylic acid radicals generally found
useful are those having 2 to 10 or more carbon atoms. Although
carboxylic acid radicals having more than about 10 carbon atoms can
be used in the invention they are generally less desirable than the
lower molecular weight carboxylic acid radicals. Typical saturated
aliphatic acid radicals include the radicals of acetic acid,
propionic acid, butyric acid, pentanoic acid, 3 methylhexanoic
acid, succinic acid, malonic acid, etc. Typical unsaturated
aliphatic acid radicals include the radicals of acrylic acid,
allylic acid, maleic acid, fumaric acid, etc. The aromatic acid
radicals which can be conveniently used in the invention include
the unsubstituted or alkyl-substituted radicals of benzoic acid,
the phthalic acids, etc. Typical alkyl-substituted aromatic acid
radicals include the radicals of methylbenzoic acid,
dimethylbenzoic acid, methylphthalic acid, etc. Preferred
carboxylic acid radicals are the saturated aliphatic carboxylic
acid radicals having 2 to 6 carbon atoms, including acetic acid,
propionic acid and butyric acid radicals.
Suitable carboxylic acid ester radicals include the alkyl ester or
partial ester radicals of any of the above acids. Typical ester
radicals are those having 1 to 6 alkyl alcohol moiety carbon atoms
and 2 to 10 acid moiety carbon atoms, i.e., 3 to 16 total carbon
atoms. Typical ester radicals include methyl acetate, ethyl
acetate, hexyl propionate, butyl succinate dimethyl malonate,
ethylmethyl adipate, dimethyl maleate, methyl benzoate, etc.,
radicals. Preferred ester radicals are the alkyl ester radicals of
saturated aliphatic carboxylic acids having 1 to 4 alcohol moiety
carbon atoms and 2 to 6 acid moiety carbon atoms, i.e. 3 to 10
total carbon atoms. Preferred alkyl ester radicals include methyl
acetate, methyl propionate, ethyl butyrate, butyl pentanoate, etc.
radicals.
Suitable water soluble alkali or alkaline earth metal carboxylic
acid salts include the salts of any of the above-identified acid
radicals. The alkali and alkaline earth metals which generally form
water-soluble salts of carboxylic acids include sodium, potassium,
lithium, beryllium, magnesium, calcium, etc. Typical carboxylic
acid salt radicals include sodium acetate, potassium propionate,
magnesium acetate, sodium succinate, potassium benzoate, etc.
radicals. Carboxylic acid radicals of mixed salts and partial salts
are also contemplated. Preferred cations are sodium, potassium and
magnesium. Preferred carboxylic acid salt radicals include the
salts of saturated aliphatic carboxylic acid radicals having 2 to 6
carbon atoms, such as sodium acetate, potassium acetate, magnesium
acetate, sodium propionate, potassium butyrate, sodium pentanoate,
etc. radicals.
Some aromatic triazole and imino compounds are commercially
available. Others can be manufactured by any of the known methods
for making these compounds. The preparation of the aromatic
triazoles and imino compounds useable in this invention forms no
part of the invention.
The compositions of the invention can be prepared by blending the
components. The method of preparation of the compositions of the
invention is not critical. A convenient method of preparation is to
dissolve or disperse the components in water to produce an aqueous
concentrate containing about 10 to 30% active components.
The amount of corrosion inhibitor composition used in an
application will depend upon the characteristics of the operating
systems and the quality of the water used in the system. In
general, the amounts used will be a matter of choice. Very small
amounts are effective in inhibiting corrosion. The upper limit is
determined by economics and practical considerations. In general, a
sufficient amount of corrosion inhibitor is usually used to provide
aromatic triazole and imino compound concentrations of about 0.01
to 250 ppm each and more. Commonly the concentration of each of
these components is maintained in the range of about 0.1 to 50 ppm,
based on the total weight of aqueous medium in the system. The
ratio of aromatic triazole to imino compound in the compositions of
the invention is not critical and can be tailored to meet specific
requirements. Popular ratios are in the range of about 95 to 50
parts of aromatic triazole to 50 to 5 parts of imino compound. More
commonly, ratios are in the range of about 90 to 70 parts by weight
of aromatic triazole to 30 to 10 parts of imino compound.
The corrosion inhibitor can be introduced into the system in any
desired manner and at any desired location. It is often preferred
to introduce the corrosion inhibitor at points just upstream of the
equipment to be protected. A proportionating pump or other
injection means can be used to introduce the corrosion inhibitor
into the system.
Other additives may be added to the corrosion inhibiting
compositions of the invention, if desired. For example, other
corrosion inhibitors, dispersants, buffering agents, antifoulants,
etc. may be incorporated into the corrosion inhibiting
compositions.
The invention is exemplified by the following specific working
examples. Unless otherwise indicated, parts and percentages are on
a weight basis.
The examples were carried out according to the following procedure.
The corrosion experiments were run in a cell comprised of a 600 ml
tallform beaker into which was inserted a copper coupon 1/2 inch
wide by 3 inches long by 1/16 inch thick. The copper coupon was
Series 110 electrolytic copper. 400 ml of solution was added to the
beaker. The solution was a water mixture of the treatment chemicals
and sodium hypochlorite. The water used was a filtered tap water
having the analysis listed in TABLE I. The copper ion was added as
cupric chloride. The solution in the beaker was stirred with a
magnetic stirrer except during the actual measurement of corrosion.
Prior to use the copper coupons were immersed in an inhibited HC1
solution , water washed, burnished with a Nylon.RTM. pad, rinsed
with acetone and air dried. Chlorine was added to the test
solutions as sodium hypochlorite. The concentration of available
chlorine was determined by an Orion Specific chlorine electrode
using an Orion pH meter Model 900.
The experimental design was a matrix in which the pH of the
solution and the concentration of inhibitor were independent
variables as shown in TABLE II. The corrosion in terms of mils/year
(mpy) is tabulated in the boxes of TABLE II. The coupons were
immersed in the test solutions for twenty-four hours at 37.degree.
C. Corrison rates were determined using a Princeton Applied
Research Model 350-A Corrosion Measuring System. The Stern-Geary
method was used to determine the corrosion rate.
EXAMPLE I (Comparative)
Various corrosion experiments were carried out in accordance with
the above procedure. In the experiments, methylbenzotriazole was
added to the test solutions at concentrations varying from 0 to 5
ppm. The corrosion rates were determined at pH's ranging from 6.0
to 8.0. Each system contained 0.5 ppm of copper II ion and an
available chlorine content of 5 ppm (calculated as Cl.sub.2). The
results are tabulated in TABLE II.
EXAMPLE II
The procedure of Example I was repeated except that iminodiacetic
acid was added to the test solutions in amounts to provide a
constant methylbenzotriazole to iminodiacetic acid ratio of 4:1.
The results are tabulated in TABLE II.
TABLE I ______________________________________ Water Analysis
______________________________________ Calcium.sup.++ (CaCO.sub.3)
106 ppm Cupric (Cu.sup.++) ion.sup.1 5 ppm Iron (as soluble iron)
0.08 ppm Phosphate ion 0.45 ppm Sulfate ion 110 ppm Chloride ion 39
ppm Total Hardness (CaCO.sub.3) 160 ppm
______________________________________ .sup.1 The Cu.sup.++ ion was
added to the test solution as cupric chloride.
TABLE II ______________________________________ Inhibitor
Concentration, ppm Corrosion Rate, mpy pH Run 0 1 2 3 4 5
______________________________________ 6.0 1 .366 .377 .262 .172
.189 .138 2 .225 .164 .179 .134 .127 6.5 1 .213 .525 .399 .295 .217
.079 2 .737 .085 .297 .111 .057 7.0 1 .568 .273 .317 .232 .239 .143
2 .084 .016 .232 .213 .045 7.5 1 .249 .939 .228 .201 .280 1.39 2
.236 .084 .155 .048 .103 8.0 1 .359 1.509 3.4 .26 .445 .39 2 .627
.490 .209 .207 .104 ______________________________________
Table II shows the results obtained using methylbenzotriazole at
various concentrations. In the number 1 runs the
methylbenzotriazole was used alone, and in the number 2 runs the
methylbenzotriazole was used in combination with iminodiacetic acid
at a methylbenzotriazole to imminodiacetic acid weight ratio of
4:1. Comparisons of the number 1 and number 2 runs at each pH and
inhibitor concentration level shows that the corrosion rate is, in
almost all cases, significantly lower when the iminodiacetic acid
is used in combination with the methylbenzotriazole.
Although the invention is illustrated with particular reference to
specific examples, it is understood that the invention is not
limited thereto. Variations are included within the scope of the
invention. For example, the corrosion inhibitors may be used in
combination with the imino acids described herein, and the
corrosion inhibiting compositions of the invention may be used in
other systems. The scope of the invention is limited only by the
breadth of the appended claims.
* * * * *